We extend the black hole (BH) feedback models of Ciotti, Ostriker, and Proga to two dimensions. In this paper, we focus on identifying the differences between the one-dimensional and two-dimensional hydrodynamical simulations. We examine a normal, isolated L * galaxy subject to the cooling flow instability of gas in the inner regions. Allowance is made for subsequent star formation, Type Ia and Type II supernovae, radiation pressure, and inflow to the central BH from mildly rotating galactic gas which is being replenished as a normal consequence of stellar evolution. The central BH accretes some of the infalling gas and expels a conical wind with mass, momentum, and energy flux derived from both observational and theoretical studies. The galaxy is assumed to have low specific angular momentum in analogy with the existing one-dimensional case in order to isolate the effect of dimensionality. The code then tracks the interaction of the outflowing radiation and winds with the galactic gas and their effects on regulating the accretion. After matching physical modeling to the extent possible between the one-dimensional and two-dimensional treatments, we find essentially similar results in terms of BH growth and duty cycle (fraction of the time above a given fraction of the Eddington luminosity). In the two-dimensional calculations, the cool shells forming at 0.1-1 kpc from the center are Rayleigh-Taylor unstable to fragmentation, leading to a somewhat higher accretion rate, less effective feedback, and a more irregular pattern of bursting compared to the one-dimensional case.

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The deposition of mechanical feedback from a supermassive black hole (SMBH) in an active galactic nucleus (AGN) into the surrounding galaxy occurs via broad-line winds which must carry mass and radial momentum as well as energy. The effect can be summarized by the dimensionless parameteris the efficiency by which accreted matter is turned into wind energy in the disc surrounding the central SMBH. The outflowing mass and momentum are proportional to η, and many prior treatments have essentially assumed that η = 0. We perform one-and two-dimensional simulations and find that the growth of the central SMBH is very sensitive to the inclusion of the mass and momentum driving but is insensitive to the assumed mechanical efficiency. For example in representative calculations, the omission of momentum and mass feedback leads to an hundred fold increase in the mass of the SMBH to over 10 10 M ⊙ . When allowance is made for momentum driving, the final SMBH mass is much lower and the wind efficiencies which lead to the most observationally acceptable results are relatively low with ǫ w 10 −4 .

There is strong evidence that the mass in the Universe is dominated by dark matter, which exerts gravitational attraction but whose exact nature is unknown. In particular, all galaxies are believed to be embedded in massive haloes of dark matter. 1,2 This view has recently been challenged by surprisingly low random stellar velocities in the outskirts of ordinary elliptical galaxies, which were interpreted as indicating a lack of dark matter. 3,4 Here we show that the low velocities are in fact compatible with galaxy formation in darkmatter haloes. Using numerical simulations of disc-galaxy mergers, 5,6 we find that the stellar orbits in the outer regions of the resulting ellipticals are very elongated. These stars were torn by tidal forces from their original galaxies during the first close passage and put on outgoing trajectories. The elongated orbits, combined with the steeply falling density profile of the observed tracers, explain the observed low velocities even in the presence of large amounts of dark matter. Projection effects when viewing a triaxial elliptical can lead to even lower observed velocities along certain lines of sight. IntroductionThe common spiral galaxies are known to reside in extended dark-matter (DM) haloes. The rotational speeds of their gas discs do not decline outside the visible body, 1 unlike the expectation from Keplerian circular velocities at a radius r about a mass M, V 2 = GM/r. Thus, the DM mass within r is growing roughly as M(r) ∝ r and it dominates the gravitational potential beyond a certain radius. An extrapolation based on the typical halo density profile 7 found in simulations of the standard ΛCDM cosmology predicts an outer "virial" radius R vir that is 50-100 times larger than the characteristic stellar radius, enclosing 10-20 times more DM than luminous matter, now also indicated observationally.. 8 2 Dekel et al.The conventional wisdom is that the potential wells created by the DM are crucial for seeding the formation of galaxies. 2,9,10 The standard hypothesis is that ellipticals originate from mergers of discs 11 and should therefore be embedded in similar DM haloes. There is evidence for DM in giant ellipticals, from X-rays 12 and gravitational lensing 13 and in nearby dwarf galaxies from stellar kinematics. 14 However, ordinary ellipticals lack obvious velocity tracers at the large projected radii r p where the DM is expected to be important. This is typically beyond R eff , 15 the "effective" radius encompassing half the projected light, while measurements of the projected velocity dispersion σ p of the stellar light are limited to r p < 2R eff .The strong [OIII] emission line at 5007Å from Planetary Nebulae (PN) -hot shells of gas expelled from dying stars of (1 − 3)M ⊙ -provide a unique tool for extracting σ p (r p ) beyond R eff . Romanowsky et al. 4 measured σ p from ∼100 bright PNs in each of three normal ellipticals, NGC 821, 3379 and 4494, adding to 531 PNs in NGC 4697 by Mendez et al.. 3 They find that σ p typically drops by a factor ≃ 1.6 between r...

We address the correlations of black hole (BH) mass with four different hostgalaxy properties from 11 existing data sets. For the purpose of guiding theoretical understanding, we first try to quantify the tightness of the intrinsic correlations. We assume that all of the relations are power laws and perform linear regressions that are symmetric in the two variables on the logarithms of the data points. Given the estimated measurement errors, we evaluate the probability distribution of the residual variance in excess of that expected from the measurement errors. Our central result is that the current data sets do not allow definite conclusions regarding the quality of the true correlations because the obtained probability distributions for the residual variance overlap for most quantities. Velocity dispersion as collected by Merritt and Ferrarese (σ MF ) and galaxy light concentration as measured by Graham and coworkers (C Re ) are consistent with zero residual variance. Taken at face value, this means that these two correlations are better than the others, but this conclusion is highly sensitive to the assumed measurement errors and would be undone if the present estimated errors were too large. We then consider which of the relations offer the best inferences of BH mass when there is no direct measurement available. As with the residual variances, we find that the probability distribution of expected uncertainty in inferred BH masses overlaps significantly for most of the relations. Photometric methods would then be preferred because the data are easier to obtain, as long as bulge-disk decomposition or detailed modeling of the photometric profile (as studied by Graham and coworkers do not present problems. Determining which correlation offers the best inferences requires reducing the uncertainty in the expected error in the inferred BH masses (the "error on the error"). This uncertainty is currently limited by uncertainty in the residual variance for all of the relations. The only quantities for which BH mass inferences are limited by measurement error are σ MF and C Re . Therefore, if these relations are truly better than the others, then new, improved measurements should allow improved inferences of BH masses. If they do not, the conclusion must be that the present low residual variances for these two relations result from overestimated error bars.A second question is which correlation allows the most accurate inferences of BH mass